Interlock for safety switches



April 22. 1924. 1,490,935

- E. MILLER INTERLOCK FOR SAFETY SWITCHES Filed April 18 1921 Patented Apr. 22 1924.

. uurrs o T es PATENT oFnca.

mumsr MILLER, or LOSTANYGELES, cam-rem.-

mrmocxgron SAFETY swrronns.

a imauonmedja rii 1a, 1921. Serial No. 462,235.

To all whom it may concern:

Be it known that I Enrms'r MILLER, a citizen of the United tat'es, residing at Los Angeles, in'the county of Los Angeles and b State of California, have invented a new and useful Interlock, for Safety Switches, of

which th followin is a specification.

My invention re ates to electric switches such as are commonly used as service switches between the line of the electric power producer and I the premises of the individual consumers;

My invention has a peculiar utility when used at theentrance to buildings andwhile readily adaptable for other purposes, the following description will be restricted in a measure to this particular use. It is necessary wherever a power companys-lines enter a building to provide a switch by which the service to that building may .beentirely disconnected. It has been the practice for many years to supply open type knife switches for this purpose. These switches are extremely dangerous both as fire and life hazards as they have exposed live parts which a person maycome in contact with and which may be short-circuited by accidental contact with metal members.

The power companies are attempting to replace these open switches with enclosed switches, that is to say, with switches which are entirely inside a metal box having a hingedcover. By enclosing the switches in a metal box, the dan r of accidental con-' tact is considerabl r uced. It is still,.how-

ever, possible w ere the ordinary knife switch is simply placed in a cabinet for accidents to happen especially as the consumer may leave the box open and it has become the practice to provide an operating handle on the outside of the box so that the switch can be opened and closed without danger of the operator coming in contact with any live part of the switch, andso that it is not nec- .essary for him to open the box in the ordinary operation of the switch.

It is, however, common practice to place( fuses inside thev box and the box must be opened for renewal of these fuses in case they are blown. Safety boxes are, therefore, manufactured in which the ffusesvare placed on the deadside of the switch and in which. the cover is interlocked .With theswitch in such a manner that. the switch must be opened before the cover is opened, thus in suring that practically all of the live parts of the switch shall be dead before the cover is opened and in which the switch is inter- .made evident hereinafter.

, In the drawing which is for illustrative purposes only, r

. F'g. 1 is a cross section through a switch box embodying my invention. I i

Fig. 2 is a side view showing the handle. .Fig.' 3 is a plan view of the interlock mechanism. proper. i i I Fig. 4 is an end view of the box. Fig. 5. is a view of how the mechanism disengages the door latch.

(Flg. 6 is a view showing the mechanism latch engaged due to the opening of the door, and,

. Fig. 7 is a view showing the mechanism liatch disengaged dueto the closing of the oor.

Inthis drawing, 11 is the box, 12 isthe cover and 13 is the hinge for the cover. The switch is mounted on an insulating base 20, and consists of fuse clips 21, enclosed fuses 22, hin e jaws 23, break jaws 24 and blades 25. e blades are pivoted at 26 in the hinge jaws 23 and carry a cross bar 27 on their free ends. Secured to the cross bar 27 is a bracket 28 to which a link 29 is pivoted by a pin 30. I The link 29 has a slot 31 at one endthrough which an operating rod 32 pames- This operating rod 32 passes through the side of the box 11 as shown in Fig. 4, and is bent up and over the switch passing through the hub 35 of the handle 36 being outside of the box. The handle 36 and the journal end 37 of the member 32 turn about a center 38indicated in Fig. 1 which isabove and outside of the pivot 26 of the switch. A tension spring 39 is secured to an eye 40 on the link 29 and to the operating member 32. Mounted on a pivot 40 on the. side ,ofthe switch is a sheet metal member 41.,formi'ng'a cover latch 42 and a mechanism latch 43. The cover latch 42 may engage vahook 44, carried on the cover 12, and a tensionspring'fi is provided which tends to draw the latch 42 into engagement with the hook 44 and which also tends to draw the latch 43 into engagement with the operating bar 32 when the switch is open. This will be better understood from a description of the method of operation which is as follows:

The switch being closed or in the position shown in full lines in Fig. 1 and the cover being closed withthe member 41 in the position shown in full lines in that figure, it is evident that the cover is locked by the hook 42. The cover being locked, it cannot be opened so long as the switch is closed. For the purpose of opening the switch, the operator grasps the handle 37 and moves it from the position shown in full lines in Fig. 2 to the position shown in dotted lines in that figure. During the initial portion of this movement, the member 32 slides in the slot 31 exerting a tension on the spring 39. As soon as the member 92 reaches the end of its movement in the slot 31, it starts to positively pull upon the cross bar 27 until the friction of the break jaws 24 on the blades 25 is insuflicient to resist the tension of the spring 39 at which time the blade is pulled out of contact with the oint- 34 by the spring 39, thus providing a quick break and eliminating the tendency to are between the jaws 24 and the blades 25. The shape of the hook 43 is such that it is pushed downinto the position shown in dotted lines in Fig. 1 by the operating rod 32 when the switch is en- 4 tirely open, thus releasing the latch 44.

The cover can nowbe opened. The blades 25, the hinge joints 23, the fuse clips 21 and the switch 22 are disconnected from the cricuit and dead. The break jaws 24 are still, however, alive but are fairly well shielded by the remaining mechanism of the switch. The fuses 22 can be inspected or replaced without serious danger of accident. If, however, the user attempts toclose the switch, the spring 45 causes the latch 43 to follow up and engage the member 32 as soon as this member starts to move towards its closing position, the latch 43 thus catching and holding the rod 32 and preventing the switch from being closed while the cover is open. If, however, the cover is closed, the hook 44 pushes the latch 42 back far enough to release the latch 43 and the switch may be closed.

I claim as my invention:

1. In a safety switch having a case, a cover for said case,'and a mechanism inside said case, the combination of acylindrical pivot; a member having a cylindrical hole fitting on said pivot; a cover latch formed on said member; a mechanism latch formed onfs'aid member; a spring tending to throw each of said latches into engagement; means ,by

which the mechanism when open throws the lmh of g nt "with and cover; and means by which the cover when closed throws the mechanism latch out of engagement with said mechanism.

2. In a safety latch having a casing, a cover for said case, and a mechanism inside said case, the combination of a cylindrical ivot; a member having a cylindrical hole fitting on said pivot; a cover latch formed on said member; a mechanism latch formed on said member; a spring tending to throw each of said latches into engagement; an arm on said mechanism pressing against said member and throwing said cover latch out of engagement with said cover when said mechanism is in the open position; and means by which the cover when closed throws the mechanism latch out of engagement with said mechanism.

3. In a safety latch havin a casing, a cover for said case, and a mec anism inside said case, the combination of a cylindrical pivot; a member having a cylindrical hole fitting on said pivot; a cover latch formed on said member; a mechanism latch formed on said member; a spring tending to throw each of said latches into engagement; means by which the mechanism when open throws the cover latch out of engagement with said cover; and a hook carried by said cover and so shaped that it throws said mechanism latch out of engagement with said mechanism when said cover is closed.

4. In a safety switch having a case, a cover for said case, and a mechanism inside said case, the combination of a cylindrical pivot; a member having a cylindrical hole fitting on said pivot; a cover latch formed on said member; a mechanism latch formed on said member; a'spring tending to throw each of said latches into engagement; an arm on said mechanism pressing against said member and throwing said cover latch out of engagement with said cover when said mechanism is in the open position and a hook carried by said cover and so shaped that it throws said mechanism latch out of engagement with said mechanism when said cover is closed.

5. In 'a safety switch having a case, a cover for said case, and a mechanism inside said case, the combination. of a cylindrical pivot: a member having a cylindri'cal hole fitting on said pivot; a cover latch formed on said member; a mechanism latch formed on said member; a tension spring having one end secured to said case and the other secured to member in such a manner as to tend to force said cover latch and said mechanism latch into engagement; means by which the mechanism when open "throws the cover latch out of engagement with's'aid cover; and means by which the cover when closed throws the mechanism latch but "of engagement with .said mechanism.

' gagement with said cover when said mecha-' tting on said pivot; a cover latch formed on said member; a mechanism latch formed on said member; a tensionsprin having one end secured to said case and t e other secured to member in such a manner as to tend to 'force said cover latch and said mechanism latch into engagement; an arm on said mechanism pressing against said member and throwing said cover latch'out of ennism isin the open osition; and meansby which the cover w en closed throws the mechanism latch cut of engagement with said mechanism. W i a 7. In a safety latch having a casing, a cover forsaid case, and a mechanism inside said case, the combination of a cylindrical pivot; a member having a cylindrical hole fitting on said pivot; a cover latch formed on said member; a mechanism latch formed on said member a tension spring having one end secured to said caseand the other secured to member in such a manner as to tend to force said cover latch and said mechanism into engagement; means by which the mechanism when open throws the cover latch out of engagement with said cover; and a hook carried by said cover and so shaped that it throws said mechanism latch out of engagement with said mechanism when said cover is closed.

8. In a safety switch having a case, a cover for said case, and a mechanism inside said case, the combination of a cylindrical ivot; a member having a cylindrical hole tting on said pivot; a cover latch formed on said member; a mechanism latch formed on said member; a tension spring having one end secured to said case and the other se- 'my hand at Los Angeles, California, this 9th day of March,

- ERNEST MILLER.

Miami 

